IB Physics Quiz: Concluding And Evaluating
20 questions · exam conditions
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Concluding And EvaluatingQuestion 1 of 20

In an experiment to verify Ohm's law for a metallic conductor, a student uses an ammeter that has a systematic zero error, causing it to always read 0.1 A higher than the true current. The student takes readings of voltage (V) and current (I) and calculates the resistance R for each pair using R = V/I. How does this error affect the calculated values of resistance?

How does the zero error in the ammeter affect the student's calculated values for resistance?

The calculated resistance will be systematically higher than the true value.
The calculated resistance will be systematically lower than the true value.
The error will be random, affecting the precision but not the overall accuracy of the average resistance.
The error will not affect the calculated resistance because the added current is constant for all readings.
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IB Physics Quiz

IB Physics Quiz: Concluding And Evaluating

Practice Concluding And Evaluating in IB Physics with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Concluding And Evaluating, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Physics.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

In an experiment to verify Ohm's law for a metallic conductor, a student uses an ammeter that has a systematic zero error, causing it to always read 0.1 A higher than the true current. The student takes readings of voltage (V) and current (I) and calculates the resistance R for each pair using R = V/I. How does this error affect the calculated values of resistance?

How does the zero error in the ammeter affect the student's calculated values for resistance?

  1. The calculated resistance will be systematically higher than the true value.
  2. The calculated resistance will be systematically lower than the true value. (correct answer)
  3. The error will be random, affecting the precision but not the overall accuracy of the average resistance.
  4. The error will not affect the calculated resistance because the added current is constant for all readings.
Explanation: The resistance is calculated using the formula R = V/I. The measured current, I_measured, is equal to the true current, I_true, plus a constant offset: I_measured = I_true + 0.1 A. Since the measured current is in the denominator of the resistance calculation and is always larger than the true current, the calculated resistance (R = V/I_measured) will be systematically lower than the true resistance for all measurements.

Question 2

Two groups of students measure the specific heat capacity of aluminum. The accepted value is 900 J kg⁻¹ K⁻¹. Group 1 obtains a result of (910 ± 40) J kg⁻¹ K⁻¹. Group 2 obtains a result of (950 ± 5) J kg⁻¹ K⁻¹.

Which of the following is the best evaluation of these two results?

  1. Group 1's result is accurate and precise, while Group 2's is inaccurate and imprecise.
  2. Group 2's result is better than Group 1's because its percentage uncertainty is much smaller.
  3. Group 1's result is consistent with the accepted value, while Group 2's is more precise but not consistent with it. (correct answer)
  4. Both results are inaccurate because neither of their mean values is exactly 900 J kg⁻¹ K⁻¹.
Explanation: Accuracy refers to how close a result is to the accepted value, considering uncertainty. Group 1's range [870, 950] includes the accepted value of 900, so it is accurate. Group 2's range [945, 955] does not include 900, so it is inaccurate. Precision refers to the size of the uncertainty. Group 2's result (±5) is more precise than Group 1's (±40). Therefore, Group 1's result is accurate but less precise, while Group 2's is precise but inaccurate.

Question 3

In a photoelectric effect experiment, a student plots a graph of the maximum kinetic energy (E_k,max) of emitted photoelectrons on the y-axis against the frequency (f) of the incident light on the x-axis. The data points form a straight line.

What fundamental physical constant can be determined by calculating the gradient of this graph?

  1. The elementary charge, e.
  2. The speed of light, c.
  3. The Planck constant, h. (correct answer)
  4. The work function of the metal, Φ.
Explanation: The photoelectric effect is described by Einstein's equation: E_k,max = hf - Φ. This equation is in the form of a straight line, y = mx + c, where y = E_k,max, x = f, the gradient m = h, and the y-intercept c = -Φ. Therefore, the gradient of a graph of E_k,max versus f gives an experimental value for the Planck constant, h.

Question 4

An experiment is conducted to determine the spring constant, k, of a spring using the relationship F = kx. A student measures the extension x for different applied forces F. When reading the position of the marker on the vertical ruler, the student's eye level varies, sometimes being slightly above and sometimes slightly below the marker.

What is the most accurate evaluation of the effect of this parallax error on the conclusion?

  1. It introduces a systematic error, causing the calculated value of k to be consistently too high.
  2. It introduces a systematic error, causing the graph of F versus x to not pass through the origin.
  3. It introduces a random error in x, which reduces the precision of the determined value of k. (correct answer)
  4. It introduces a random error in x, which reduces the accuracy of k but does not affect its precision.
Explanation: Parallax error, where the observer's eye level is not consistently perpendicular to the scale, leads to readings that can be either too high or too low in an unpredictable way. This is the definition of a random error. Random errors increase the scatter of data points around the line of best fit. This uncertainty in the data leads to a reduced precision (i.e., a larger uncertainty) in the value of the gradient, which in an F versus x graph represents the spring constant k.

Question 5

Upon analyzing a Hertzsprung-Russell (HR) diagram, a student concludes that a star's mass must directly cause its surface temperature, because the main sequence shows a clear trend of more massive stars being hotter.

Which statement best evaluates the student's conclusion about causation?

  1. The conclusion is correct, as higher mass leads to stronger gravitational pressure, which in turn causes higher core and surface temperatures.
  2. The conclusion mistakes correlation for causation; mass, temperature, and luminosity are all correlated, but the fundamental property is the star's chemical composition.
  3. The conclusion is an oversimplification; a star's mass is the primary factor determining its core fusion rate, which in turn determines its luminosity and surface temperature. (correct answer)
  4. The conclusion is backward; a star's high surface temperature is what allows it to maintain its large mass against gravitational collapse.
Explanation: While there is a causal link, the student's statement is too direct. A star's initial mass is the most fundamental property that dictates its entire life cycle. The mass determines the gravitational pressure at the core, which sets the rate of nuclear fusion. This fusion rate determines the star's energy output (luminosity) and the resulting surface temperature needed to radiate that energy away. So, mass causes the fusion rate, which in turn causes the temperature and luminosity. The student's conclusion is an oversimplification of this chain of causation.

Question 6

In an experiment to verify the conservation of linear momentum, the total momentum of a system of two carts before a collision is calculated to be (0.45 ± 0.03) kg m s⁻¹. After the collision, the total momentum is (0.48 ± 0.03) kg m s⁻¹.

What is the most appropriate conclusion to draw from these results?

  1. Momentum has not been conserved because the final momentum is greater than the initial momentum.
  2. The experiment contains a systematic error that causes the measured momentum to increase.
  3. The results support the law of conservation of momentum as the initial and final values agree within their uncertainties. (correct answer)
  4. The collision must have been perfectly elastic for momentum to be conserved this closely.
Explanation: To check for consistency, we see if the ranges of the two values overlap. The initial momentum range is [0.42, 0.48] kg m s⁻¹. The final momentum range is [0.45, 0.51] kg m s⁻¹. Since these two ranges overlap (specifically, from 0.45 to 0.48), the values are considered to be in agreement within experimental uncertainty. Therefore, the data supports the conclusion that momentum was conserved.

Question 7

To determine the resistivity of a metal, a student measures the resistance of wires of different lengths from the same spool. During each measurement with a digital multimeter, they notice that the resistance reading starts low and increases slightly over a few seconds before stabilizing.

Based on this observation, what is the most important uncontrolled variable that the student must evaluate?

  1. The heating of the wire due to the current from the multimeter. (correct answer)
  2. The contact resistance between the multimeter probes and the wire.
  3. The uniformity of the wire's cross-sectional area along its length.
  4. The ambient humidity of the laboratory affecting the wire's surface.
Explanation: The resistance of a metal is dependent on its temperature, generally increasing as temperature rises. The multimeter measures resistance by passing a small current through the wire. This current causes Joule heating (P = I²R), which raises the wire's temperature. The observation that the resistance increases and then stabilizes is a classic sign of the wire heating up and reaching a new thermal equilibrium. This change in temperature is an uncontrolled variable that systematically affects the resistance measurement.

Question 8

A student makes the statement: "Since modern physics shows that atoms are mostly empty space, the solid nature of a table is just an illusion."

From the perspective of physics, what is the best evaluation of this statement?

  1. The statement is misleading; the perception of solidity is caused by electrostatic repulsion between the electron clouds of atoms. (correct answer)
  2. The statement is incorrect; the solidity of the table is due to the strong nuclear force holding the nuclei together.
  3. The statement is correct; solidity is a subjective human perception, not a physical property.
  4. The statement is correct because the Pauli exclusion principle is not a real force, but a quantum mechanical property.
Explanation: While atoms are mostly empty space, the conclusion that solidity is an illusion is misleading. The macroscopic property of 'solidity' and the inability to pass one object through another is a very real physical phenomenon. It is caused by the powerful electrostatic repulsion between the negatively charged electron clouds of the atoms in the table and the atoms in a hand, for example. The Pauli exclusion principle also plays a crucial role in preventing electron orbitals from overlapping. These effects, not the nucleus or a lack of forces, create the experience of solidity.

Question 9

A manufacturer claims their new thermometer is both highly accurate and highly precise. An engineer tests it by placing it in a bath of boiling water at standard atmospheric pressure (100.0 °C). The thermometer gives the following five readings: 101.5 °C, 101.6 °C, 101.5 °C, 101.4 °C, 101.5 °C.

Which is the best evaluation of the thermometer based on these data?

  1. It is accurate but not precise.
  2. It is precise but not accurate. (correct answer)
  3. It is both accurate and precise.
  4. It is neither accurate nor precise.
Explanation: Precision refers to the repeatability or consistency of measurements. The readings are all very close to each other (ranging only from 101.4 to 101.6), so the thermometer is precise. Accuracy refers to how close the measurements are to the true value. The true value is 100.0 °C, but the readings are consistently around 101.5 °C, a significant deviation. Therefore, the thermometer is not accurate. It has a systematic error.

Question 10

A student uses the standard kinematic equations, which assume no air resistance, to predict the range of a projectile. In a corresponding experiment, the student finds that the measured range is consistently 8% shorter than the range predicted by the model. The measurements of initial velocity and angle have a combined uncertainty of 3%.

What is the most valid conclusion based on this outcome?

  1. The student's measurements must contain a large systematic error that reduces the measured range.
  2. The kinematic model is inadequate for this situation because it neglects a significant factor, such as air resistance. (correct answer)
  3. The discrepancy is fully explained by the random uncertainties in the initial measurements.
  4. The value of acceleration due to gravity, g, used in the model was likely incorrect for the location.
Explanation: The discrepancy (8%) between the model and the experiment is larger than the measurement uncertainty (3%). Furthermore, the discrepancy is systematic (consistently shorter). This suggests that the model itself is the issue. The standard kinematic model for projectiles neglects air resistance, which is a dissipative force that reduces the range. Therefore, the most likely conclusion is that the model is inadequate because this factor is significant.

Question 11

A student performs an experiment to measure the acceleration due to gravity, g, using a simple pendulum. Their final result is calculated as g = (9.8 ± 0.5) m s⁻². The accepted value for their location is 9.81 m s⁻². The student concludes that their experiment was accurate. Which of the following is the best evaluation of this conclusion?

  1. The conclusion is not justified because the experimental value is not exactly 9.81 m s⁻².
  2. The conclusion is justified because the accepted value lies within the range of the experimental uncertainty. (correct answer)
  3. The conclusion is not justified because the percentage uncertainty of the measurement is too large.
  4. The conclusion is justified because the experimental value of 9.8 m s⁻² is very close to the accepted value of 9.81 m s⁻².
Explanation: Accuracy is an assessment of how close a measurement is to the true or accepted value. An experimental result is considered accurate if the accepted value falls within the bounds of the experimental uncertainty. Here, the experimental range is from 9.3 m s⁻² to 10.3 m s⁻². Since 9.81 m s⁻² is within this range, the conclusion that the experiment is accurate is justified.

Question 12

A student drops a ball from rest and measures its velocity v after it has fallen through a height h. They plot the ball's kinetic energy (E_k) against h. According to the principle of conservation of energy without air resistance, this graph should be a straight line (E_k = mgh). The student's data produces a curve whose gradient decreases as h increases.

What is the most plausible conclusion that can be drawn from this curved graph?

  1. The acceleration due to gravity, g, decreases as the ball falls.
  2. A constant amount of energy was lost to thermal energy for every meter the ball fell.
  3. Energy was not conserved because of a systematic error in the velocity sensor.
  4. The dissipative force of air resistance increased as the ball's speed increased. (correct answer)
Explanation: The gradient of an E_k vs h graph represents the net downward force doing work on the ball. If there were no air resistance, the gradient would be constant and equal to mg. A decreasing gradient means the net downward force is decreasing. This happens because as the ball falls from greater heights (larger h), its speed increases. Air resistance is a force that opposes motion and its magnitude increases with speed. Therefore, the net force (mg - F_air) decreases, and the rate at which kinetic energy is gained with respect to height also decreases.

Question 13

A student is designing an experiment to investigate how the force (F) on a current-carrying wire in a uniform magnetic field depends on the angle (θ) between the wire and the field lines. The student plans to vary the angle and measure the resulting force.

To ensure a valid conclusion about the relationship between F and θ, which experimental condition is most critical to evaluate and maintain?

  1. The precision of the protractor used to measure the angle θ must be very high.
  2. The length of the wire that is inside the magnetic field must be kept constant at all angles. (correct answer)
  3. The magnetic field must be perfectly uniform throughout the entire region of the apparatus.
  4. The current in the wire must be supplied by a battery rather than a variable power supply.
Explanation: The relationship is given by F = BIL sin(θ). To investigate the dependence of F on θ, all other variables (B, I, L) must be controlled and kept constant. The length L in the equation refers specifically to the length of the wire within the magnetic field. As the angle θ is changed, it is easy to inadvertently change this length. Therefore, ensuring L remains constant is a critical control for the experiment's validity.

Question 14

A student measures the activity of a radioactive sample using a Geiger counter. Over a period of one minute, the total count recorded is 1200. One hour later, the student measures again for one minute and records a total count of 1180. The student concludes that the sample has a very long half-life, which can be calculated from this small decrease.

What is the primary reason this conclusion is likely to be invalid?

  1. The background radiation count was not subtracted from the measurements.
  2. The decrease in counts is so small that it cannot be reliably distinguished from the inherent random fluctuations of radioactive decay. (correct answer)
  3. The student should have measured the activity in Becquerels, not counts per minute.
  4. An hour is too long an interval between measurements, allowing for external factors to change.
Explanation: Radioactive decay is a random, probabilistic process. The number of decays in a given interval fluctuates statistically. For a count of N, the statistical uncertainty is approximately √N. For the first count of 1200, the uncertainty is about √1200 ≈ 35. For the second count of 1180, it is √1180 ≈ 34. The observed decrease of 20 is well within the range of expected random fluctuations. Therefore, it is impossible to conclude that this small change represents the actual decay of the sample rather than statistical noise.

Question 15

A student investigates the relationship between the period T and length l of a simple pendulum, predicted by the equation T = 2π√(l/g). To find g, they plot a graph of T² versus l. The theoretical expectation is a straight line passing through the origin. The student's line of best fit is straight but has a small, positive y-intercept.

What is the most likely conclusion that can be drawn from the positive y-intercept on the T² versus l graph?

  1. Random errors in timing the period T were the dominant source of uncertainty.
  2. The value of g at the student's location is significantly different from the standard value.
  3. Air resistance had a significant and consistent effect on the pendulum's motion.
  4. There was a systematic error in measuring the length, such that the effective length was always greater than the measured length. (correct answer)
Explanation: The equation can be written as T² = (4π²/g)l. If the effective length is l_eff = l_measured + c, where c is a small constant offset (e.g., from the pivot point not being a true point), then T² = (4π²/g)(l_measured + c) = (4π²/g)l_measured + (4π²/g)c. When plotting T² vs l_measured, the term (4π²/g)c is a constant positive y-intercept. Random errors would cause scatter, and a different value of g would change the gradient, not create an intercept. Air resistance would likely introduce non-linearity.

Question 16

A researcher investigates the relationship between the intensity, I, of light from a small source and the distance, r, from the source. The inverse square law, I ∝ 1/r², is hypothesized. The researcher measures an intensity of (16 ± 1) units at distance r, and an intensity of (5 ± 1) units at distance 2r. The researcher concludes the inverse square law is not supported.

What is the best evaluation of the researcher's conclusion?

  1. The conclusion is invalid because the intensity at 2r should have been 8 units, not 4 units.
  2. The conclusion is correct because the measured intensity at 2r is clearly higher than the predicted value of 4 units.
  3. The conclusion is premature because the predicted value of 4 units lies within the experimental uncertainty of the measurement at 2r. (correct answer)
  4. The conclusion is correct because only two data points are insufficient to verify any physical law.
Explanation: According to the inverse square law, if the intensity at distance r is 16 units, the intensity at distance 2r should be 16 / 2² = 4 units. The researcher measured the intensity at 2r to be (5 ± 1) units, which corresponds to a range of [4, 6] units. Since the predicted value of 4 units falls within this uncertainty range, the data is actually consistent with the inverse square law. Therefore, the conclusion that the law is not supported is premature.

Question 17

A student concludes that their experimental data proves Boyle's Law (PV = constant) for a sample of air. The data was collected using a standard school laboratory gas syringe and pressure sensor.

What is a necessary evaluation of the student's conclusion regarding the 'proof' of Boyle's Law?

  1. The conclusion is valid, as experiments are the primary way physical laws are proven to be correct.
  2. The conclusion is flawed because Boyle's Law only applies to ideal gases, and air is a real gas.
  3. The conclusion should be that the data is consistent with Boyle's Law within the limits of experimental uncertainty. (correct answer)
  4. The conclusion is invalid unless the experiment was repeated at least five times with identical results.
Explanation: In science, experiments do not 'prove' a law with absolute certainty. They can only provide evidence that supports or is consistent with a law. A student's experiment, with its inherent uncertainties and limitations, can at best show that the data follows the predicted relationship within the bounds of those uncertainties. Therefore, the correct scientific language is to conclude that the results are 'consistent with' or 'support' the law, rather than 'proving' it.

Question 18

A student aims to verify the relationship between the fundamental frequency (f) of a vibrating string and its tension (T). The theoretical model predicts that f² is directly proportional to T. The student takes measurements and wants to produce a linear graph to confirm the relationship.

Which graph should the student plot and what feature would provide the strongest evidence for the predicted relationship?

  1. A graph of f² versus T, which should be a straight line passing through the origin. (correct answer)
  2. A graph of log(f) versus log(T), which should be a straight line with a gradient of 2.
  3. A graph of f versus T, which should be a straight line through the origin.
  4. A graph of f versus T², which should be a straight line passing through the origin.
Explanation: To linearize the relationship f² ∝ T, we can write it as f² = kT, where k is the constant of proportionality. This equation is in the form y = mx, where y = f², x = T, and the gradient m = k. A graph of f² on the y-axis versus T on the x-axis should therefore produce a straight line. Because the relationship is a direct proportionality, the line should also pass through the origin (zero tension should result in zero frequency). This provides the most direct graphical test of the stated relationship.

Question 19

A student measures the pressure P of a fixed mass of gas at various temperatures T (in Celsius). They plot a graph of P versus T, obtain a straight line of best fit, and extrapolate it back to the T-axis. They conclude that the intercept value represents absolute zero.

What is the most significant limitation of this experimental conclusion?

  1. The extrapolation assumes the gas will continue to behave as an ideal gas at very low temperatures, which is not true. (correct answer)
  2. Any random errors in the pressure measurements will make the extrapolated value for absolute zero inaccurate.
  3. The student should have plotted pressure against temperature in kelvin to obtain a meaningful result.
  4. The conclusion is only valid if the volume of the gas was perfectly constant throughout the experiment.
Explanation: The primary issue with this method is the large extrapolation from laboratory temperatures (e.g., 0-100°C) down to approximately -273°C. This extrapolation implicitly assumes that the linear relationship (Charles's Law) holds over this entire range. In reality, any real gas will liquefy and then solidify long before it reaches absolute zero, and its behavior will deviate significantly from the ideal gas model. This physical limitation is more significant than the effects of measurement uncertainty.

Question 20

In a Young's double-slit experiment to determine the wavelength of light (λ), the formula s = λD/d is used, where s is the fringe separation, D is the slit-to-screen distance, and d is the slit separation. The final calculated value of λ has a large percentage uncertainty.

Assuming the absolute uncertainty in each measurement (Δs, ΔD, Δd) is fixed, which change to the experimental setup would be most effective in reducing the percentage uncertainty of λ?

  1. Using a light source with a significantly shorter wavelength.
  2. Using a double-slit grating with a much larger slit separation, d.
  3. Decreasing the distance, D, from the slits to the screen.
  4. Increasing the distance, D, from the slits to the screen. (correct answer)
Explanation: The percentage uncertainty in λ is approximately the sum of the percentage uncertainties of s, D, and d. To reduce the overall percentage uncertainty, we should aim to reduce the largest of these individual terms. The percentage uncertainty of s is Δs/s. By increasing D, the fringe separation s (s = λD/d) increases. Since Δs (the absolute uncertainty in measuring s, e.g., ±0.5 mm on a ruler) is fixed, increasing s decreases the ratio Δs/s. This is often the most effective way to improve the precision of the result.